1. Field of the Invention
This invention relates to an improved process for manufacturing d,l-alpha-tocopherol.
2. Description of the Prior Art
The preparation of d,l-alpha-tocopherol by the condensation of trimethylhydroquinone and a phytol derivative in the presence of an inert solvent and acid condensing agents is well known in the art. The acid catalyst can be either or both a Lewis acid such as zinc chloride or a strong inorganic acid such as hydrochloric acid, sodium bisulfate or para-toluenesulfonic acid. In addition, it is known from U.S. Pat. No. 4,191,692 to pre-react isophytol with a small amount of ammonia or an amine prior to reaction with trimethylhydroquinone.
The use of zinc chloride, an inert solvent and gaseous hydrochloric acid in the process of producing d,l-alpha-tocopherol is disclosed by Karrer in U.S. Pat. Nos. 2,411,967; 2,411,968; and 2,411,969. Greenbaum et al in U.S. Pat. No. 3,708,505 also disclose the use of a combination of a Lewis acid and a strong acid in a process for the preparation of d,l-alpha-tocopherol.
Improved process catalysts or combinations thereof are also disclosed in U.S. Pat. Nos. 4,208,334; 2,723,278; 3,789.086; 3,459,773; 3,444,213; and 4,217,285.